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Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

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Page 1: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

Forecasting using Discrete Event Simulation for the NZ Prison Population

Dr Jason (Qingsheng) Wang

Mr Ross Edney

Ministry of Justice

Page 2: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

2

Prison Population Projections

• The prison population in NZ has grown steadily over the last decade

• The prisoner population is the end result of a chain of complex causal factors

• Serious crime, apprehensions, investigations, prosecutions and court cases which can involve variable periods of remand are precursors to imprisonment

• The opportunity cost of excess prison beds is high

• The costs of bed shortages is also high due in part to risks to staff and prisoner safety

• Several years of planning is required to build a prison so accurate forecasts are important

Page 3: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

3

Discrete Event Simulation (DES)

• DES treats each prisoner entering the prison system separately and assigns the time that will be spent in prison so there is an entry date and exit date

• The technique “releases” prisoners from the virtual prison system when they have served their sentence

• DES can support multiple inflows • A forecast track for the prisoner population can be

derived by using the inflow and stay-time data

Page 4: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

4

Remand Prison Population DES Model and Its Direct Drivers

• Remand prisoner inflows/arrivals

• Time spend on remand

month

start

t y

Set A(5)

daily rate

F

Rmonth

Remand

CT SF

0

numbersinRemand Inflow

Time on Remand

F

R

Remand Prison

A

Get

Remand

F

Rmonth

3

RA

Exit#

171318DI

LUF PW

Page 5: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

5

Sentenced Prison Population DES Model and Its Direct Drivers

• Sentenced prisoner inflows/arrivals

• Given sentence for each arrived prisoners

• Proportion of sentence served

month

start

t y

A: <=3M

Set A(5)

Given sent length

F

R

month

A: <=3M

CT SF

0

Proportion served

F

R

A

Get

Daily rate

month

A: <=3M

F

RF

R

Sentenced Prison

Sentenced Inflow A

ChangeA

month

A: <=3M

RA

Exit#

119209DI

LUF PW

3

Page 6: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

6

Determining Forecast Assumptions

• Historic data is employed to derive key input assumptions

• Time series and expert opinion is used to form a view of the likely direction of key driver variables

• Experts provide independent input on the impact of new policy that may affect, for example, custodial sentences and their length during the forecast horizon

Page 7: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

7

2006 Forecast, Sentenced Inflow

Inflows/Arrivals by Sentence GroupSentenced, Male

0

100

200

300

400

500

600

700

Jun-

98

Dec

-98

Jun-

99

Dec

-99

Jun-

00

Dec

-00

Jun-

01

Dec

-01

Jun-

02

Dec

-02

Jun-

03

Dec

-03

Jun-

04

Dec

-04

Jun-

05

Dec

-05

Jun-

06

Dec

-06

Jun-

07

Dec

-07

Jun-

08

Dec

-08

Jun-

09

Dec

-09

Jun-

10

Dec

-10

Jun-

11

Dec

-11

Jun-

12

Dec

-12

Jun-

13

Dec

-13

Jun-

14

Arrival, <=1Y Arrival, >1Y to 2Y Arrival, >2Y Arrival, SV

Inflow/Arrivals Time-Series Projections

Page 8: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

8

2006 Forecast, Proportion Served

Projected Proportion Served (excl Remand) for > 2Y Non-SV, Male

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Jun-

98

Oct

-98

Feb

-99

Jun-

99

Oct

-99

Feb

-00

Jun-

00

Oct

-00

Feb

-01

Jun-

01

Oct

-01

Feb

-02

Jun-

02

Oct

-02

Feb

-03

Jun-

03

Oct

-03

Feb

-04

Jun-

04

Oct

-04

Feb

-05

Jun-

05

Oct

-05

Feb

-06

Jun-

06

Oct

-06

Feb

-07

Jun-

07

Oct

-07

Feb

-08

Jun-

08

Oct

-08

Feb

-09

Jun-

09

Oct

-09

Feb

-10

Jun-

10

>2Y to 3Y >3Y to 5Y >5Y Proj E: >2Y to 3Y Proj F: >3Y to 5Y Proj G: >5Y

Page 9: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

9

2006 Forecast, Male Sentenced

Simulation Projections with Assumptions of Baseline Scenario Sentenced Male

0

500

1000

1500

2000

2500

Jun-

98

Dec

-98

Jun-

99

Dec

-99

Jun-

00

Dec

-00

Jun-

01

Dec

-01

Jun-

02

Dec

-02

Jun-

03

Dec

-03

Jun-

04

Dec

-04

Jun-

05

Dec

-05

Jun-

06

Dec

-06

Jun-

07

Dec

-07

Jun-

08

Dec

-08

Jun-

09

Dec

-09

Jun-

10

Dec

-10

Jun-

11

Dec

-11

Jun-

12

Dec

-12

Jun-

13

Dec

-13

Jun-

14

Muster, <=1Y Muster, >1Y to 2Y Muster, >2Y Muster, SV Muster, Life&PD

Sim Proj Baseline, <=1Y Sim Proj Baseline, >1Y to 2Y Sim Proj Beseline, >2Y Sim Proj Baseline, SV Time-series Proj, Life&PD

Page 10: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

10

2006 Forecast, Male Remand

Simulation Projection with Assumptions of Baseline Scenario Remand Male

0

500

1,000

1,500

2,000

2,500

3,000

Jun-

98

Dec

-98

Jun-

99

Dec

-99

Jun-

00

Dec

-00

Jun-

01

Dec

-01

Jun-

02

Dec

-02

Jun-

03

Dec

-03

Jun-

04

Dec

-04

Jun-

05

Dec

-05

Jun-

06

Dec

-06

Jun-

07

Dec

-07

Jun-

08

Dec

-08

Jun-

09

Dec

-09

Jun-

10

Dec

-10

Jun-

11

Dec

-11

Jun-

12

Dec

-12

Jun-

13

Dec

-13

Jun-

14

Remand Muster, Male Simulation, Baseline Proj, Male

Page 11: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

11

2006 Forecast Performance,Including EI after New Sentences

Total Prison Population

6000

6500

7000

7500

8000

8500

9000

9500

1-J

an-0

71

5-J

an

-07

29-J

an

-07

12-F

eb

-07

26-F

eb

-07

12-M

ar-

07

26-M

ar-

07

9-A

pr-

07

23-A

pr-

07

7-M

ay-

07

21-M

ay-

07

4-J

un-0

71

8-J

un

-07

2-J

ul-0

71

6-J

ul-

07

30-J

ul-

07

13-A

ug-0

72

7-A

ug-0

71

0-S

ep-0

72

4-S

ep-0

78

-Oct

-07

22-O

ct-0

75

-No

v-07

19-N

ov-

07

3-D

ec-

07

17-D

ec-

07

31-D

ec-

07

14-J

an

-08

28-J

an

-08

11-F

eb

-08

25-F

eb

-08

10-M

ar-

08

24-M

ar-

08

7-A

pr-

08

21-A

pr-

08

5-M

ay-

08

19-M

ay-

08

2-J

un-0

81

6-J

un

-08

30-J

un

-08

14-J

ul-

08

28-J

ul-

08

11-A

ug-0

82

5-A

ug-0

88

-Se

p-0

82

2-S

ep-0

86

-Oct

-08

20-O

ct-0

83

-No

v-08

17-N

ov-

08

1-D

ec-

08

15-D

ec-

08

29-D

ec-

08

Date

Pri

so

ner

da

ily c

ou

nt

Maximum Justice beds available to Corrections (Police Cells)

Maximum Corrections operating capacity

Total actual Prison population

Average daily operating capacity

2006 Justice Sector Forecast

Monday peak 7,848

Spring Hill opens - phased occupancy

Page 12: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

12

DES Monte-Carlo Model, Confidence Intervals, and Capacity Planning Buffer

• Instead of using fixed mean values, the distributional DES model will feed the direct drivers with distributional values.

• Monte Carlo simulation will generate the population/muster probability distribution so to identify peak demand and risks over the planning horizon

• Policy simulation: this approach can be applied in policy changes with distributional impact

Page 13: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

13

Sentenced Distributional DES Model

F

R

CT SF

year

Time on remand distributions

Set A(5)

Input table:

daily rate

Remand Male

Remand Inflow distributions

Remand Prison

F

R

month

1

F

Rmonth

3

RA

A

Get

DI

LUF PW

Exit#

190035

F

R

change

run#

month

Writes results

Page 14: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

14

Remand Monthly Inflow and Distribution

• Using normal distribution of Holt-Winters model residuals and prediction errors

-500

0

500

1,000

1,500

2,000

2,500

1-J

un

-98

1-D

ec-9

8

1-J

un

-99

1-D

ec-9

9

1-J

un

-00

1-D

ec-0

0

1-J

un

-01

1-D

ec-0

1

1-J

un

-02

1-D

ec-0

2

1-J

un

-03

1-D

ec-0

3

1-J

un

-04

1-D

ec-0

4

1-J

un

-05

1-D

ec-0

5

1-J

un

-06

1-D

ec-0

6

1-J

un

-07

1-D

ec-0

7

1-J

un

-08

1-D

ec-0

8

1-J

un

-09

1-D

ec-0

9

1-J

un

-10

1-D

ec-1

0

1-J

un

-11

1-D

ec-1

1

1-J

un

-12

1-D

ec-1

2

1-J

un

-13

1-D

ec-1

3

1-J

un

-14

1-D

ec-1

4

1-J

un

-15

RESIDUAL

ACTUAL

FORECAST

STD

L95

U95

Drop Page Fields Here

Sum of MRem_Inflow

Date

_TYPE_

Page 15: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

15

Time on Remand Distributions• Annual empirical distributions

Projection o f T im e on Rem and Distributions, M ale

0%

5%

10%

15%

20%

25%

30%

35%

01:Up to 07days

02:Up to 14days

03:Up to 21days

04:Up to 28days

05:Up to 35days

06:Up to 49days

07:Up to 84days

08:Up to 189days

09:Up to 364days

10:Morethan 364

days

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

2015

2016

Page 16: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

16

Remand Muster Monte-Carlo, Male

Male Remand Distributional Model's Monte-Carlo v3, Inflow-Normal & Time-on-Empirical

0

500

1000

1500

2000

2500

3000

3500

4000

4500

Oct-95 Jul-98 Apr-01 Jan-04 Oct-06 Jul-09 Apr-12 Dec-14 Sep-17

1 2 34 5 67 8 910 11 1213 14 1516 17 1819 20 2122 23 2425 26 2728 29 3031 32 3334 35 3637 38 3940 41 4243 44 4546 47 4849 50 5152 53 5455 56 5758 59 6061 62 6364 65 6667 68 6970 71 7273 74 7576 77 7879 80 8182 83 8485 86 8788 89 9091 92 9394 95 9697 98 99100 101 102103 104 105106 107 108109 110 111112 113 114115 116 117118 119 120121 122 123124 125 126127 128 129130 131 132133 134 135136 137 138139 140 141142 143 144145 146 147148 149 150

Page 17: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

17

Muster Distribution Normality TestCross-Section Distributions, Remand

500 Runs of Male Remand Distributional Model v3 based on Inflow-Normal & Time-on-Empirical Distributions

Std Kurtosis Skewness Jarque-Bera testχ²(JB,2) Remand muster cross section distribution at July-199937.03036 0.060376 0.040828 0.21485 0.898144

Bin FrequencyCumulative %Normal Cumulative %Rem Dis Normal Dis594 2 0.4% 0% 0% 0%619 9 2.2% 2% 2% 2%644 33 8.8% 9% 7% 7%669 86 26.0% 25% 17% 16%694 117 49.4% 50% 23% 25%719 137 76.8% 75% 27% 25%744 68 90.4% 91% 14% 16%769 39 98.2% 98% 8% 7%794 7 99.6% 100% 1% 2%819 1 99.8% 100% 0% 0%

More 1 100.0%

Std Kurtosis Skewness Jarque-Bera testχ²(JB,2) Remand muster cross section distribution at July-200039.03053 -0.045201 -0.169691 2.442145 0.294914

Bin FrequencyCumulative %Normal Cumulative %Rem Dis Normal Dis704 2 0.4% 0% 0% 0%730 14 3.2% 2% 3% 2%756 37 10.6% 9% 7% 7%782 69 24.4% 25% 14% 16%808 123 49.0% 50% 25% 25%834 130 75.0% 75% 26% 25%860 85 92.0% 91% 17% 16%886 31 98.2% 98% 6% 7%912 7 99.6% 100% 1% 2%938 2 100.0% 100% 0% 0%

More 0 100.0%

Std Kurtosis Skewness Jarque-Bera testχ²(JB,2) Remand muster cross section distribution at July-200138.70658 -0.123777 0.08981 0.991343 0.609162

Bin FrequencyCumulative %Normal Cumulative %Rem Dis Normal Dis733 2 0.4% 0% 0% 0%758 8 2.0% 3% 2% 2%783 38 9.6% 10% 8% 7%808 91 27.8% 26% 18% 16%833 124 52.6% 50% 25% 24%858 109 74.4% 74% 22% 24%883 83 91.0% 90% 17% 16%908 31 97.2% 97% 6% 7%933 11 99.4% 100% 2% 2%958 2 99.8% 100% 0% 0%

More 1 100.0%

0%

5%

10%

15%

20%

25%

30%

1 2 3 4 5 6 7 8 9 10

Rem Dis Normal Dis

0%

5%

10%

15%

20%

25%

30%

1 2 3 4 5 6 7 8 9 10

Rem Dis Normal Dis

0%

5%

10%

15%

20%

25%

30%

1 2 3 4 5 6 7 8 9 10

Rem Dis Normal Dis

Page 18: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

18

Standardised Monte-Carlo, Remand

Normalised Monte-Carlo, Remand Male v3 (Inflow-Normal & Time-On-Empirical)

-5.00

-4.00

-3.00

-2.00

-1.00

0.00

1.00

2.00

3.00

4.00

5.00

Oct-95 Jul-98 Apr-01 Jan-04 Oct-06 Jul-09 Apr-12 Dec-14 Sep-17

1 23 45 67 89 1011 1213 1415 1617 1819 2021 2223 2425 2627 2829 3031 3233 3435 3637 3839 4041 4243 4445 4647 4849 5051 5253 5455 5657 5859 6061 6263 6465 6667 6869 7071 7273 7475 7677 7879 8081 8283 8485 8687 8889 9091 9293 9495 9697 9899 100

Page 19: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

19

Standardised Monte-Carlo’s Distributions, Remand

Normalised Monte-Carlo, Remand Male v3 (Inflow-Normal & Time-On-Empirical)

From Jun-98 to Aug-07

Std Kurtosis Skewness Jarque-Bera testχ²(JB,2)0.99901 -0.004549 0.0323931 9.753995 0.0076199

BinObservatio

ns

Rem Cumulative

%

Normal Cumulative

%Rem Dis Normal Dis

-4 1 0.0% 0.0% 0.0% 0.0%-3 63 0.1% 0.1% 0.1% 0.1%-2 1,142 2.2% 2.3% 2.1% 2.1%-1 7,605 15.9% 15.8% 13.7% 13.6%0 19,108 50.3% 50.0% 34.4% 34.2%1 18,696 84.0% 84.2% 33.7% 34.2%2 7,602 97.7% 97.7% 13.7% 13.6%3 1,203 99.9% 99.9% 2.2% 2.1%4 79 100.0% 100.0% 0.1% 0.1%5 1 100.0% 100.0% 0.0% 0.0%

More 0 100%55,500

From Sep-07 to Aug-15

Std Kurtosis Skewness Jarque-Bera testχ²(JB,2)0.99901 0.0307374 -0.0024895 1.98 0.3716581

BinObservatio

ns

Rem Cumulative

%

Normal Cumulative

%Rem Dis Normal Dis

-4 3 0.0% 0.0% 0.0% 0.0%-3 72 0.2% 0.1% 0.2% 0.1%-2 1,013 2.3% 2.3% 2.1% 2.1%-1 6,523 15.9% 15.8% 13.6% 13.6%0 16,345 49.9% 50.0% 34.1% 34.2%1 16,422 84.1% 84.2% 34.2% 34.2%2 6,524 97.7% 97.7% 13.6% 13.6%3 1,034 99.9% 99.9% 2.2% 2.1%4 63 100.0% 100.0% 0.1% 0.1%5 1 100.0% 100.0% 0.0% 0.0%

More 0 100.0%48,000

-5.0%

0.0%

5.0%

10.0%

15.0%

20.0%

25.0%

30.0%

35.0%

40.0%

1 2 3 4 5 6 7 8 9 10

Rem Dis Normal Dis

0.0%

5.0%

10.0%

15.0%

20.0%

25.0%

30.0%

35.0%

40.0%

1 2 3 4 5 6 7 8 9 10

Rem Dis Normal Dis

Page 20: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

20

Standardised Monte-Carlo Distribution, Sentenced

Normalised Monte-Carlo, Sentenced Male v2 (Inflow Normal, Given Sentence &PropServ Empirical)

From Jun-98 to Aug-07

Std Kurtosis Skewness Jarque-Bera testχ²(JB,2)0.999008 -0.079553 0.02493332 20.385624 3.74385E-05

BinObservatio

ns

Sent Cumulative

%

Normal Cumulative

%Sent Dis Normal Dis

-4 3 0.01% 0.0% 0.01% 0.00%-3 41 0.08% 0.1% 0.07% 0.13%-2 1161 2.17% 2.3% 2.09% 2.13%-1 7646 15.95% 15.8% 13.78% 13.58%0 19017 50.21% 50.0% 34.26% 34.16%1 18701 83.91% 84.2% 33.70% 34.16%2 7669 97.73% 97.7% 13.82% 13.58%3 1190 99.87% 99.9% 2.14% 2.13%4 69 99.99% 100.0% 0.12% 0.13%5 3 100.00% 100.0% 0.01% 0.00%

More 0 100.00%55,500

1.000972714

From Sep-07 to Aug-15

Std Kurtosis Skewness Jarque-Bera testχ²(JB,2)0.99901 -0.013876 -0.0488389 19.47 5.93E-05

BinObservatio

ns

Sent Cumulative

%

Normal Cumulative

%Sent Dis Normal Dis

-4 8 0.02% 0.0% 0.0% 0.0%-3 67 0.16% 0.1% 0.1% 0.1%-2 1057 2.36% 2.3% 2.2% 2.1%-1 6592 16.09% 15.8% 13.7% 13.6%0 15978 49.38% 50.0% 33.3% 34.2%1 16659 84.09% 84.2% 34.7% 34.2%2 6523 97.68% 97.7% 13.6% 13.6%3 1086 99.94% 99.9% 2.3% 2.1%4 30 100.00% 100.0% 0.1% 0.1%5 0 100.00% 100.0% 0.0% 0.0%

More 0 100.00%48,000

1.2815516

0.00%

5.00%

10.00%

15.00%

20.00%

25.00%

30.00%

35.00%

40.00%

-4 -3 -2 -1 0 1 2 3 4 5

Sent Dis Normal Dis

0.0%

5.0%

10.0%

15.0%

20.0%

25.0%

30.0%

35.0%

40.0%

1 2 3 4 5 6 7 8 9 10

Sent Dis Normal Dis

Normal Dis

0%

5%

10%

15%

20%

25%

30%

35%

40%

-4 -3 -2 -1 0 1 2 3 4 5

Normal Dis

Page 21: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

21

Forecast Confidence Intervals with Normal Distribution and Empirical Distribution

Mean Forecast with 90% Confidence Intervals of Normal & Empirical Distributions, Male Total

6,500

7,000

7,500

8,000

8,500

9,000

9,500

10,000

10,500

11,000

11,500

Sep

-07

Dec

-07

Mar

-08

Jun-

08

Sep

-08

Dec

-08

Mar

-09

Jun-

09

Sep

-09

Dec

-09

Mar

-10

Jun-

10

Sep

-10

Dec

-10

Mar

-11

Jun-

11

Sep

-11

Dec

-11

Mar

-12

Jun-

12

Sep

-12

Dec

-12

Mar

-13

Jun-

13

Sep

-13

Dec

-13

Mar

-14

Jun-

14

Sep

-14

Dec

-14

Mar

-15

Jun-

15

Male Musters Mean Forecast Upper 90%, Normal Dis Lower 90%, Normal Dis Upper 90%, Empirical Dis Lower 90%, Empirical Dis

Page 22: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

22

Volatility Buffer Calculation Assuming Normal Distributions

Male Prison Bed's Buffer Calculation, 1 STD for Optimal Pricing of BS Model

0

100

200

300

400

500

600

700

800

Sep

-07

Dec

-07

Mar

-08

Jun-

08

Sep

-08

Dec

-08

Mar

-09

Jun-

09

Sep

-09

Dec

-09

Mar

-10

Jun-

10

Sep

-10

Dec

-10

Mar

-11

Jun-

11

Sep

-11

Dec

-11

Mar

-12

Jun-

12

Sep

-12

Dec

-12

Mar

-13

Jun-

13

Sep

-13

Dec

-13

Mar

-14

Jun-

14

Sep

-14

Dec

-14

Mar

-15

Jun-

15

0%

1%

2%

3%

4%

5%

6%

7%

8%

Rem Buffer Calculation (1 Std) Sent Buffer Calculation (1 Std) % Buffer Calculation

Page 23: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

23

End

•Thank you

Page 24: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

24

Jarque-Bera Test, Remand

Jarque-Bera Normality Test, Male Remand v3 (Inflow-Normal & Time-On-Empirical)

0.000

0.100

0.200

0.300

0.400

0.500

0.600

0.700

0.800

0.900

1.000

Jun-

98

Dec-9

8

Jun-

99

Dec-9

9

Jun-

00

Dec-0

0

Jun-

01

Dec-0

1

Jun-

02

Dec-0

2

Jun-

03

Dec-0

3

Jun-

04

Dec-0

4

Jun-

05

Dec-0

5

Jun-

06

Dec-0

6

Jun-

07

Dec-0

7

Jun-

08

Dec-0

8

Jun-

09

Dec-0

9

Jun-

10

Dec-1

0

Jun-

11

Dec-1

1

Jun-

12

Dec-1

2

Jun-

13

Dec-1

3

Jun-

14

Dec-1

4

Jun-

15

?²(JB,2)

Page 25: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

25

Sentenced Distributional DES ModelInflows and Distributions

-200

-100

0

100

200

300

400

500

600

700

800

900

1-J

un-9

8

1-D

ec-

98

1-J

un-9

9

1-D

ec-

99

1-J

un-0

0

1-D

ec-0

0

1-Ju

n-0

1

1-D

ec-0

1

1-Ju

n-0

2

1-D

ec-0

2

1-Ju

n-03

1-D

ec-0

3

1-Ju

n-04

1-D

ec-0

4

1-Ju

n-05

1-D

ec

-05

1-J

un-

06

1-D

ec

-06

1-J

un-

07

1-D

ec-

07

1-J

un-0

8

1-D

ec-

08

1-J

un-0

9

1-D

ec-

09

1-J

un-1

0

1-D

ec-

10

1-J

un-1

1

1-D

ec-

11

1-J

un-1

2

1-D

ec-1

2

1-Ju

n-1

3

1-D

ec-1

3

1-Ju

n-1

4

1-D

ec-1

4

1-Ju

n-15

1-D

ec-1

5

RESIDUAL

ACTUAL

FORECAST

STD

L95

U95

Drop Page Fields Here

Sum of Le1Y

sentgp2

_TYPE_

<=1Y Forecast with Step Changes and Multiplicative Seasonality

0

100

200

300

400

500

600

Jun-

98

Dec

-98

Jun-

99

Dec

-99

Jun-

00

Dec

-00

Jun-

01

Dec

-01

Jun-

02

Dec

-02

Jun-

03

Dec

-03

Jun-

04

Dec

-04

Jun-

05

Dec

-05

Jun-

06

Dec

-06

Jun-

07

Dec

-07

Jun-

08

Dec

-08

Jun-

09

Dec

-09

Jun-

10

Dec

-10

Jun-

11

Dec

-11

Jun-

12

Dec

-12

Jun-

13

Dec

-13

Jun-

14

Dec

-14

Jun-

15

Dec

-15

Actual New forecast w ith step changes

-100

-50

0

50

100

150

200

250

300

1-Ju

n-98

1-D

ec-9

8

1-Ju

n-99

1-D

ec-9

9

1-Ju

n-00

1-D

ec-0

0

1-Ju

n-01

1-D

ec-0

1

1-Ju

n-02

1-D

ec-0

2

1-Ju

n-03

1-D

ec-0

3

1-Ju

n-04

1-D

ec-0

4

1-Ju

n-05

1-D

ec-0

5

1-Ju

n-06

1-D

ec-0

6

1-Ju

n-07

1-D

ec-0

7

1-Ju

n-08

1-D

ec-0

8

1-Ju

n-09

1-D

ec-0

9

1-Ju

n-10

1-D

ec-1

0

1-Ju

n-11

1-D

ec-1

1

1-Ju

n-12

1-D

ec-1

2

1-Ju

n-13

1-D

ec-1

3

1-Ju

n-14

1-D

ec-1

4

1-Ju

n-15

1-D

ec-1

5

RESIDUAL

ACTUAL

FORECAST

STD

L95

U95

Drop Page Fields Here

Sum of Y1to2Y

sentgp2

_TYPE_

>1Y to 2Y Forecast with Step Changes and Multiplicative Seasonality

0

20

40

60

80

100

120

140

160

180

200

Jun-

98

Dec

-98

Jun-

99

Dec

-99

Jun-

00

Dec

-00

Jun-

01

Dec

-01

Jun-

02

Dec

-02

Jun-

03

Dec

-03

Jun-

04

Dec

-04

Jun-

05

Dec

-05

Jun-

06

Dec

-06

Jun-

07

Dec

-07

Jun-

08

Dec

-08

Jun-

09

Dec

-09

Jun-

10

Dec

-10

Jun-

11

Dec

-11

Jun-

12

Dec

-12

Jun-

13

Dec

-13

Jun-

14

Dec

-14

Jun-

15

Dec

-15

Actual New forecast w ith step changes

Page 26: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

26

Sentenced Distributional DES ModelGiven Sentence Distributions

The Emprical Distributions of Given Sentences for <=1Y by Jun-Years

0%

5%

10%

15%

20%

25%

01: 1M, 31Days

02: 2M, 62Days

03: 3M, 92Days

04: 4M, 123Days

05: 5M, 153Days

06: 6M, 184Days

07: 7M, 214Days

08: 8M, 245Days

09: 9M, 276Days

10: 10M,306 Days

11: 11M,337 Days

12: 12M,366 Days

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

Grand Total

The Emprical Distributions of Given Sentences for >1Y to 2Y by Jun-Years

0%

5%

10%

15%

20%

25%

30%

35%

13: 1Y1M,397 Days

14: 1Y2M,427 Days

15: 1Y3M,458 Days

16: 1Y4M,489 Days

17: 1Y5M,519 Days

18: 1Y6M,550 Days

19: 1Y7M,580 Days

20: 1Y8M,611 Days

21: 1Y9M,641 Days

22: 1Y10M,671 Days

23: 1Y11M,701 Days

24: 2Y, 731Days

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

Grand Total

The Emprical Distributions of Given Sentences for >2Y Non-SV by Jun-Years

0%

10%

20%

30%

40%

50%

60%

70%

25: 3Y, 1096Days

26: 4Y, 1461Days

27: 5Y, 1827Days

28: 6Y, 2192Days

29: 7Y, 2557Days

30: 8Y, 2922Days

31: 9Y, 3288Days

32: 10Y, 3653Days

33: >10Y

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

Grand Total

The Emprical Distributions of Given Sentences for >2Y SV by Jun-Years

0%

5%

10%

15%

20%

25%

30%

35%

25: 3Y, 1096Days

26: 4Y, 1461Days

27: 5Y, 1827Days

28: 6Y, 2192Days

29: 7Y, 2557Days

30: 8Y, 2922Days

31: 9Y, 3288Days

32: 10Y, 3653Days

33: >10Y

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

Grand Total

Page 27: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

27

Sentenced Distributional DES ModelProportion Served Distributions

Proportion Sentence Served excluding Remand, Male

0%

10%

20%

30%

40%

50%

60%

70%

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9 1 0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9 1 0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9 1 0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9 1

01: <=1Y 02: >1Y to 2Y 03: >2Y 04: SV

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

Gender2 Male+

Sum of Percent

sentgp2 PropServ_asSent

End_JuneY

Page 28: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

28

Proportion Served Distributions

>2Y. Non-SV

-5%

0%

5%

10%

15%

20%

25%

30%

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

2015

SV, >2Y

-10%

0%

10%

20%

30%

40%

50%

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

2015

Page 29: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

29

Sentenced Muster Monte-Carlo, Male

Male Sentenced Distributional Model's Monte-Carlo

0

1000

2000

3000

4000

5000

6000

7000

8000

Oct-95 Jul-98 Apr-01 Jan-04 Oct-06 Jul-09 Apr-12 Dec-14 Sep-17

1 2 34 5 67 8 910 11 1213 14 1516 17 1819 20 2122 23 2425 26 2728 29 3031 32 3334 35 3637 38 3940 41 4243 44 4546 47 4849 50 5152 53 5455 56 5758 59 6061 62 6364 65 6667 68 6970 71 7273 74 7576 77 7879 80 8182 83 8485 86 8788 89 9091 92 9394 95 9697 98 99100 101 102103 104 105106 107 108109 110 111112 113 114115 116 117118 119 120121 122 123124 125 126127 128 129130 131 132133 134 135136 137 138139 140 141142 143 144145 146 147148 149 150

Page 30: Forecasting using Discrete Event Simulation for the NZ Prison Population Dr Jason (Qingsheng) Wang Mr Ross Edney Ministry of Justice

30

Jarque-Bera Test, Sentenced Male

Jarque-Bera Test, Male Sentenced v3 (Inflow-Normal, Given Sentence & PropServ Empirical)

0.000

0.100

0.200

0.300

0.400

0.500

0.600

0.700

0.800

0.900

1.000

Jun-

98

Dec-9

8

Jun-

99

Dec-9

9

Jun-

00

Dec-0

0

Jun-

01

Dec-0

1

Jun-

02

Dec-0

2

Jun-

03

Dec-0

3

Jun-

04

Dec-0

4

Jun-

05

Dec-0

5

Jun-

06

Dec-0

6

Jun-

07

Dec-0

7

Jun-

08

Dec-0

8

Jun-

09

Dec-0

9

Jun-

10

Dec-1

0

Jun-

11

Dec-1

1

Jun-

12

Dec-1

2

Jun-

13

Dec-1

3

Jun-

14

Dec-1

4

Jun-

15

?²(JB,2)